Various properties are required for a ball such as volleyball and beach volleyball. For example, surface abrasion resistance at high level is required for a surface material subjected to repeated rubbing or collision with the ground, a floor, or the like. Further, in a case where a ball is controlled directly with a hand, soft cushioning property and controllability are required for reducing impact on fingertips and/or arms in touching the ball. Further, in recent years, even when the surface of a ball gets wet with perspiration, favorable controllability is demanded in many cases.
Various methods have been hitherto proposed as a method for obtaining a ball having surface abrasion resistance and cushioning property at high level, and also having leather-like appearance and texture in terms of inclination.
For example, there are proposed: a leather-like sheet at least including 4 layers of a nonporous elastic polymer layer (first layer), a porous elastic polymer layer (second layer), a layer formed of an elastic polymer and a nonwoven fabric (third layer), and a nonwoven fabric layer (fourth layer); and a ball formed of the leather-like sheet (see Patent Document 1). However, in a method of Patent Document 1, the first and second layers are formed by using elastic polymers each having durability for practical use to provide a ball which has insufficient cushioning property and which is not satisfactory in controllability and flight performance of a ball.
Further, as a leather-like sheet having an excellent three-dimensional shape in addition to cushioning property, there is proposed: a synthetic leather having a transparent nonporous layer containing polyurethane as a main ingredient laminated on a surface of a fibrous base material covered with a polyurethane layer and having a pattern of pebbles and valleys; the synthetic leather has an air layer between the valleys and the nonporous layer; and a total area of bonding parts between the pebbles and the nonporous layer accounts for 50 to 90% of a surface area of the synthetic leather (see Patent Document 2). However, even in Patent Document 2, a ball used as a ball handled with hand(s), such as volleyball or beach volleyball, while having both cushioning property and durability for practical use has not yet been obtained, and the controllability and flight performance of the ball is not satisfactory.
In addition, there is proposed a ball having substantially continuous pebbles and valleys adjoining the pebbles formed on the surface, in which: a height difference between the pebbles and the valleys is 50 to 1,000 μm; a vertical projected area of each of the adjoining valleys is 3 to 30 mm2; an average distance between the valleys is 0.5 to 3 mm; and a total area of the vertical projected areas of the valleys accounts for 30 to 60% of a surface area of a sheet (see Patent Document 3). Such a ball is suitable as a ball caught by a hand, such as a basketball. However, as a ball hit with hand(s) such as volleyball, the impact at the time of hitting the ball, controllability, and flight performance of the ball are not satisfactory.
In addition, there is proposed a basketball which can demonstrate an excellent non-slip property even when it gets wet, due to secondary pebbles and valleys formed on the top surface of primary pebbles so that the minute pebbles and valleys of the fingerprints of hand(s) holding a ball engage with the ball (see Patent Document 4). Such a ball is suitable as a ball caught by hand(s), such as a basketball. However, as a ball hit with hand(s), such as volleyball, the impact at the time of hitting the ball, controllability, and flight performance of the ball are not satisfactory.    Patent Document 1: JP 2000-102629 A    Patent Document 2: JP 11-93081 A    Patent Document 3: WO 2005/97268 A    Patent Document 4: JP 2005-87315 A